212 lines
7.5 KiB
Markdown
212 lines
7.5 KiB
Markdown
|
If you want to write an option parser, and have it be good, there are
|
||
|
two ways to do it. The Right Way, and the Wrong Way.
|
||
|
|
||
|
The Wrong Way is to sit down and write an option parser. We've all done
|
||
|
that.
|
||
|
|
||
|
The Right Way is to write some complex configurable program with so many
|
||
|
options that you hit the limit of your frustration just trying to
|
||
|
manage them all, and defer it with duct-tape solutions until you see
|
||
|
exactly to the core of the problem, and finally snap and write an
|
||
|
awesome option parser.
|
||
|
|
||
|
If you want to write an option parser, don't write an option parser.
|
||
|
Write a package manager, or a source control system, or a service
|
||
|
restarter, or an operating system. You probably won't end up with a
|
||
|
good one of those, but if you don't give up, and you are relentless and
|
||
|
diligent enough in your procrastination, you may just end up with a very
|
||
|
nice option parser.
|
||
|
|
||
|
## USAGE
|
||
|
|
||
|
// my-program.js
|
||
|
var nopt = require("nopt")
|
||
|
, Stream = require("stream").Stream
|
||
|
, path = require("path")
|
||
|
, knownOpts = { "foo" : [String, null]
|
||
|
, "bar" : [Stream, Number]
|
||
|
, "baz" : path
|
||
|
, "bloo" : [ "big", "medium", "small" ]
|
||
|
, "flag" : Boolean
|
||
|
, "pick" : Boolean
|
||
|
, "many1" : [String, Array]
|
||
|
, "many2" : [path]
|
||
|
}
|
||
|
, shortHands = { "foofoo" : ["--foo", "Mr. Foo"]
|
||
|
, "b7" : ["--bar", "7"]
|
||
|
, "m" : ["--bloo", "medium"]
|
||
|
, "p" : ["--pick"]
|
||
|
, "f" : ["--flag"]
|
||
|
}
|
||
|
// everything is optional.
|
||
|
// knownOpts and shorthands default to {}
|
||
|
// arg list defaults to process.argv
|
||
|
// slice defaults to 2
|
||
|
, parsed = nopt(knownOpts, shortHands, process.argv, 2)
|
||
|
console.log(parsed)
|
||
|
|
||
|
This would give you support for any of the following:
|
||
|
|
||
|
```bash
|
||
|
$ node my-program.js --foo "blerp" --no-flag
|
||
|
{ "foo" : "blerp", "flag" : false }
|
||
|
|
||
|
$ node my-program.js ---bar 7 --foo "Mr. Hand" --flag
|
||
|
{ bar: 7, foo: "Mr. Hand", flag: true }
|
||
|
|
||
|
$ node my-program.js --foo "blerp" -f -----p
|
||
|
{ foo: "blerp", flag: true, pick: true }
|
||
|
|
||
|
$ node my-program.js -fp --foofoo
|
||
|
{ foo: "Mr. Foo", flag: true, pick: true }
|
||
|
|
||
|
$ node my-program.js --foofoo -- -fp # -- stops the flag parsing.
|
||
|
{ foo: "Mr. Foo", argv: { remain: ["-fp"] } }
|
||
|
|
||
|
$ node my-program.js --blatzk -fp # unknown opts are ok.
|
||
|
{ blatzk: true, flag: true, pick: true }
|
||
|
|
||
|
$ node my-program.js --blatzk=1000 -fp # but you need to use = if they have a value
|
||
|
{ blatzk: 1000, flag: true, pick: true }
|
||
|
|
||
|
$ node my-program.js --no-blatzk -fp # unless they start with "no-"
|
||
|
{ blatzk: false, flag: true, pick: true }
|
||
|
|
||
|
$ node my-program.js --baz b/a/z # known paths are resolved.
|
||
|
{ baz: "/Users/isaacs/b/a/z" }
|
||
|
|
||
|
# if Array is one of the types, then it can take many
|
||
|
# values, and will always be an array. The other types provided
|
||
|
# specify what types are allowed in the list.
|
||
|
|
||
|
$ node my-program.js --many1 5 --many1 null --many1 foo
|
||
|
{ many1: ["5", "null", "foo"] }
|
||
|
|
||
|
$ node my-program.js --many2 foo --many2 bar
|
||
|
{ many2: ["/path/to/foo", "path/to/bar"] }
|
||
|
```
|
||
|
|
||
|
Read the tests at the bottom of `lib/nopt.js` for more examples of
|
||
|
what this puppy can do.
|
||
|
|
||
|
## Types
|
||
|
|
||
|
The following types are supported, and defined on `nopt.typeDefs`
|
||
|
|
||
|
* String: A normal string. No parsing is done.
|
||
|
* path: A file system path. Gets resolved against cwd if not absolute.
|
||
|
* url: A url. If it doesn't parse, it isn't accepted.
|
||
|
* Number: Must be numeric.
|
||
|
* Date: Must parse as a date. If it does, and `Date` is one of the options,
|
||
|
then it will return a Date object, not a string.
|
||
|
* Boolean: Must be either `true` or `false`. If an option is a boolean,
|
||
|
then it does not need a value, and its presence will imply `true` as
|
||
|
the value. To negate boolean flags, do `--no-whatever` or `--whatever
|
||
|
false`
|
||
|
* NaN: Means that the option is strictly not allowed. Any value will
|
||
|
fail.
|
||
|
* Stream: An object matching the "Stream" class in node. Valuable
|
||
|
for use when validating programmatically. (npm uses this to let you
|
||
|
supply any WriteStream on the `outfd` and `logfd` config options.)
|
||
|
* Array: If `Array` is specified as one of the types, then the value
|
||
|
will be parsed as a list of options. This means that multiple values
|
||
|
can be specified, and that the value will always be an array.
|
||
|
|
||
|
If a type is an array of values not on this list, then those are
|
||
|
considered valid values. For instance, in the example above, the
|
||
|
`--bloo` option can only be one of `"big"`, `"medium"`, or `"small"`,
|
||
|
and any other value will be rejected.
|
||
|
|
||
|
When parsing unknown fields, `"true"`, `"false"`, and `"null"` will be
|
||
|
interpreted as their JavaScript equivalents.
|
||
|
|
||
|
You can also mix types and values, or multiple types, in a list. For
|
||
|
instance `{ blah: [Number, null] }` would allow a value to be set to
|
||
|
either a Number or null. When types are ordered, this implies a
|
||
|
preference, and the first type that can be used to properly interpret
|
||
|
the value will be used.
|
||
|
|
||
|
To define a new type, add it to `nopt.typeDefs`. Each item in that
|
||
|
hash is an object with a `type` member and a `validate` method. The
|
||
|
`type` member is an object that matches what goes in the type list. The
|
||
|
`validate` method is a function that gets called with `validate(data,
|
||
|
key, val)`. Validate methods should assign `data[key]` to the valid
|
||
|
value of `val` if it can be handled properly, or return boolean
|
||
|
`false` if it cannot.
|
||
|
|
||
|
You can also call `nopt.clean(data, types, typeDefs)` to clean up a
|
||
|
config object and remove its invalid properties.
|
||
|
|
||
|
## Error Handling
|
||
|
|
||
|
By default, nopt outputs a warning to standard error when invalid values for
|
||
|
known options are found. You can change this behavior by assigning a method
|
||
|
to `nopt.invalidHandler`. This method will be called with
|
||
|
the offending `nopt.invalidHandler(key, val, types)`.
|
||
|
|
||
|
If no `nopt.invalidHandler` is assigned, then it will console.error
|
||
|
its whining. If it is assigned to boolean `false` then the warning is
|
||
|
suppressed.
|
||
|
|
||
|
## Abbreviations
|
||
|
|
||
|
Yes, they are supported. If you define options like this:
|
||
|
|
||
|
```javascript
|
||
|
{ "foolhardyelephants" : Boolean
|
||
|
, "pileofmonkeys" : Boolean }
|
||
|
```
|
||
|
|
||
|
Then this will work:
|
||
|
|
||
|
```bash
|
||
|
node program.js --foolhar --pil
|
||
|
node program.js --no-f --pileofmon
|
||
|
# etc.
|
||
|
```
|
||
|
|
||
|
## Shorthands
|
||
|
|
||
|
Shorthands are a hash of shorter option names to a snippet of args that
|
||
|
they expand to.
|
||
|
|
||
|
If multiple one-character shorthands are all combined, and the
|
||
|
combination does not unambiguously match any other option or shorthand,
|
||
|
then they will be broken up into their constituent parts. For example:
|
||
|
|
||
|
```json
|
||
|
{ "s" : ["--loglevel", "silent"]
|
||
|
, "g" : "--global"
|
||
|
, "f" : "--force"
|
||
|
, "p" : "--parseable"
|
||
|
, "l" : "--long"
|
||
|
}
|
||
|
```
|
||
|
|
||
|
```bash
|
||
|
npm ls -sgflp
|
||
|
# just like doing this:
|
||
|
npm ls --loglevel silent --global --force --long --parseable
|
||
|
```
|
||
|
|
||
|
## The Rest of the args
|
||
|
|
||
|
The config object returned by nopt is given a special member called
|
||
|
`argv`, which is an object with the following fields:
|
||
|
|
||
|
* `remain`: The remaining args after all the parsing has occurred.
|
||
|
* `original`: The args as they originally appeared.
|
||
|
* `cooked`: The args after flags and shorthands are expanded.
|
||
|
|
||
|
## Slicing
|
||
|
|
||
|
Node programs are called with more or less the exact argv as it appears
|
||
|
in C land, after the v8 and node-specific options have been plucked off.
|
||
|
As such, `argv[0]` is always `node` and `argv[1]` is always the
|
||
|
JavaScript program being run.
|
||
|
|
||
|
That's usually not very useful to you. So they're sliced off by
|
||
|
default. If you want them, then you can pass in `0` as the last
|
||
|
argument, or any other number that you'd like to slice off the start of
|
||
|
the list.
|